The parameters of the annealing process will be determined by the particular alloy composition, the higher the Ni content, the hotter the temp and longer the hold time needs to be but as with all Ni alloys, it is always best to use the lowest temp possible and extending the hold time at temp to achieve the best results. GS alloy composition varies greatly but typically the Ni content is around 20-22% in good quality alloy with the balance being 46% Cu & 34% Zn, cheaper stuff has lesser amounts of Ni which, at times, can be as little as 12%.
Grain growth is the key to working with Ni/Cu alloys, the longer the hold temp, the better the grain growth and it's best to use the lowest temp possible but one must know the exact alloy composition in order to know the minimum hold temp as it will vary from 750°F to around 1420°F. Too hot a temp will cook the Zn out and heating without benefit of an atmospheric controlled furnace or similar containment will result in excessive oxidation and subsequent alloy failure. Maintaining a tight control on the hold temp is critical as fluctuations as low as ±30°F can cause intergranular separations. Quench or not to quench as well as the quench bath temp is also critical and determined by the exact alloy composition, too cold will cause grain separation and too hot will cause grain shrinkage resulting in brittleness and hardening. If quench is required or not is determined by the amount of Cu in the alloy as well as contaminating elements. In some cases an air quench is sufficient, in others the rate of cooling must be controlled.
If the bending is minimal and the alloy composition unknown, I'd take a best SWAG at saying 950-1000°F for 15-25 minutes with an air quench. See how it feels and if need be run it through another hold cycle and go to a quench bath at 90-95°F. If the amount of rework is considerable, you must identify the exact alloy or play the guessing game with the possibility of wrecking the part. Keep in mind that contaminating elements like Al, Pb, Fe, Mn and Sn in unknown alloys as the proportions of such can have a profound effect on both annealability and the alloy's cold/hot workability. As a general rule of thumb, Cu based alloys do not take kindly to hot working but those with a high Ni content can be hot-worked to a point which is usually limited to long radius bending.
I love the looks of Ni/Cu and don't mind working with it but my biggest gripe lies with suppliers that don't take the builders into consideration by identifying metal items by the exact alloy. Nothing gripes my butt more than getting parts of brass or Ni/Cu made with different alloys on the same gun. Brass isn't so bad because you can tarnish blend for the most part but there's no adjusting the color of Ni/Cu to get a match from one part to the next. The particular alloy doesn't really matter for the gun application as far as the typical design properties are concerned but it makes the world of difference in color matching and workability properties. If I was building a screw for an aircraft carrier I'd be concerned about mechanical properties but I'm not. I don't care if 60Cu/25Zn/15Ni is cheaper than the 50Cu/25Zn/25Ni alloy, I just want to know what the heck I'm getting so it matches. There's nothing worse than being in the final polishing stages and finding out the trigger guard has gold tint and the thimbles are bright nickel.
